The Ancient Highway was a series of underground passages connecting the ruins near Duck Village to the Great Hollow. These passages originally came from ancient ruins and one sealed doorway along the path led to the Ruins of Cyndar.
During the War of the Champions that particular door was sealed and the True Water Rune was hidden inside. The Lizard Clan made the most frequent use of the highway as the underground passages connected many various parts of Grassland, which they utilized to great effect in warfare.
- Genso Suikoden Kiwami Encyclopedia, page 302